How can i get into my computer??? :(?

i won a used computer from school but they didnt take any of the security settings off how would i get passed the if no user name or password work

How can i get into my computer??? :(?antivirus programs

I would recommend you reformat/re-install Windows. If you still want to get into the system first reboot Windows XP in safe mode by re-starting the computer and pressing F8 repeated as the computer starts up. Then (in safe mode) click Start and then click Run. In the open box type "control userpasswords2" without the quotes.

You will now have access to all the user accounts, including the administrators account and will be able to reset the lost password.

Just click the administrators user account, and then click Reset Password.

You will need to add a new password in the New password and the Confirm new password boxes, and confirm by clicking OK.

All done, you have recovered the lost administrators password!